Manufacture of grid electrodes



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May 16, 1967 J. G. WOEHLING MANUFACTURE OF GRID ELECTRODES 4Sheets-Sheet Filed May 20, 1964 May 16, 1967 J. G. WOEHLING 3,319,310

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United States Patent 3,319,310 MANUFACTURE OF GRID ELECTRODES John G.Woehling, Verona, N.J., assignor to Radio Corporation of America, acorporation of Delaware Filed May 20, 1964, Ser. No. 368,866 1 Claim.(Cl. 2925.18)

This invention relates to the manufacture of grid electrodes for use inelectron discharge tubes, and particularly to improvements in the stepin the manufacture of such grids known as sizing.

In certain types of grid electrodes comprising a pair of spaced apartside rods and a lateral wire wound in a helix around and secured to theside rods, it is the practice to size the grid electrodes to the desiredgrid dimensions and shape. The sizing step comprises mounting the gridaround a pair of jaws, known as sizing blades, and spreading the bladesapart. Each blade has a semicircular groove along the outer side of theblade in which a side rod is received, and the blades have a crosssection of the size and shape of the desired inner size and shape of thelateral wire helix. Upon the spreading apart of the blades, the siderods are forced apart thereby stretching the turns of the lateral wirehelix and conforming them to the shape of the blades. Also, the siderods are pressed against the walls of the grooves and straightened.

A problem long recognized in the prior art is that when grids havingside rods of resilient materials, such as molybdenum, are sized, thesizing operation is often only partially successful. The reason for thisis that if the side rods are bowed before sizing, the resilient siderods are not permanently straightened by the sizing operation, and theside rods spring back to their original bowed shape after removal of thegrid from the sizing blades. Since the lateral wire turns are stretchedand shaped to their correct dimensions while the side rods are heldstraight by the sizing blades, the rebo'wing of the side rods aftersizing causes distortion of the sized lateral wire turns. When used inelectron tubes, the grids having distorted lateral wire turns causevariations from the desired electron tube electrical characteristics.

An object of this invention is to provide an improved method offabricating grid electrodes.

A further object of this invention is to provide an improved method ofsizing grid electrodes having bowed side rod-s.

For achieving the objects of this invention, a method is providedwherein the side rods of a grid electrode are forced apart to stretchand shape the lateral wire turns, but wherein straightening of the siderods occurs only to a small extent. That is, during sizing, only certaincomponents of the side rod bow are removed or straightened, while othercomponents of the side rod bow are unaffected. Thus, upon removal of thegrid elect-rode from the sizing blades, little spring-back of the siderods to their original shape occurs due to the small amount ofstraightening of the side rods during the sizing operation. Also, in theassembly of the grid electrode into an electron tube, the side rods aremounted in such manner as to hold at least portions of the side rods insubstantially the same relative position as these side rod portions wereheld during the sizing operation.

Advantages of this method will be described in connection with thedrawings, wherein:

FIGS. 1 and 2 are end views of a grid electrode before and after thegrid has been sized;

FIG. 3 is a front elevation of a portion of apparatus which may be usedto size grid electrodes in the practice of the method of this invention.

FIG. 4 is a sectional view taken along line 44 of FIG. 3;

3 319,310 Patented May 16, 1967 FIG. 5 is a side elevation of theapparatus shown in FIG. 3;

FIGS. 6, 7, and 8 are views similar to FIGS. 3, 4, and 5, respectively,and showing an unsized grid mounted on the sizing apparatus, the bow ofthe side rods of the grid being shown exaggerated;

FIGS. 9 and 11 are views similar to FIGS. 6 and 8, respectively, andshowing a grid being sized by the apparatus;

FIG. 10 is a .plan view of the apparatus shown in FIG. 9; and

FIG. 12 is a front elevation, partly broken away, of a grid electrodemounted between a pair of spacer plates of an electrode tube, otherelectrodes of the tube not being shown.

FIGS. 1 and 2 show the effect of grid sizing on the lateral wire turns15 of a grid 16. In the winding of the grid 16 the lateral wire turns 15are wound with a generally elliptical shape (FIG. 1). After sizing (FIG.2), the lateral wire turns assume a generally rectangular shape. Also,the sizing operation slightly increases the spacing between the siderods 17 over that of the unsized grid 16.

FIGS. 3, 4, and 5 show sizing blades which may be used for sizing thegrid shown in FIG. 1 to the shape shown in FIG. 2. The blades 18 and 20are mounted on a support, not shown, which permits movement of eachblade to the right or left, as shown in FIG. 3. Spring means, not shown,bias the blades toward one another. The inner side 21 of each blade 18and 20 tapers away from the opposite blade from the top 26 to the bottom27 of the blades, and each side 21 of the blades is provided with adovetail groove 22 in which a tapered slide. 24 may move. Upon upwardmovement of slide 24 between blades 18 and 20, the blades are forcedapart in the direction of the arrows 25 shown in FIG. 3.

Slide 24 is mounted on the support used to support blades 18 and 2t} andmeans, not shown, are provided for moving slide 24 upwardly anddownwardly. A stop, not shown, is provided for limiting the upwardmovement of slide 24. Suitable blade and slide supporting and actuatingmeans are well known in the art and are not described.

The outer sides 30 of blades 18 and 20 are provided with extending lipsor walls 31 which extend almost the entire length of the blades andwhich provide side rod receiving grooves 32. Adjacent the lower ends 27and at the top ends 26 of the blades, portions 34 of the grooves 32 aresemicircular in cross section (FIG. 4). The semicircular groove portions34 are of such size as to receive portions 40 of the side rods 17adjacent the ends of the side rods relatively snuggly in the grooves andto engage about one half of the circumference of the side rods, as shownin FIGS. 10 and 11. Between the semicircular groove portions 34,portions 36 (FIGS. 4 and 5) of groove 32 are rectangular in crosssection. As shown in FIGS. 8 and 11, the rectangular groove portions 36have a width substantially greater than the diameter of side rods 17,and the bottoms of groove portions 36 make only a substantially linecontact with the side rods 17, as shown in FIG. 10.

When slide 24 is fully inserted between blades 18 and 20 (FIGS. 9, 10and 11) the blades have a size and shape corresponding to the desiredinside size and shape of the lateral wire turns 15 of the grid electrode16. Also, at this time the semi-circular groove portions 34 are spacedapart a distance equal to the spacing between the apertures in thespacer plates 44 )FIG. 12) through which the grid side rods 17 areinserted during the assembly of the grid electrode 16 into an electrontube, as known. In FIG. 12 other electrodes, such as cathode and anodeelectrodes, normally also mounted between the spacer plates 44 ofelectron tubes are not shown for reasons of clarity.

In operation, a grid 16 to be sized is mounted around the blades 18 and23 (FIGS. 6, 7, and 8) with the grid side rods 17 disposed adjacentgrooves 32 and with the side rod portions 48 disposed adjacent thesemicircular groove portions 34. At this time, as shown in FIG. 6, slide24 is in its downward position and blades 18 and 20 are in theirinwardly biased position.

As shown exaggerated in FIGS. 6 and 8, the side rods 17 are bowed, andwhen mounted on blades 18 and 219 the side rods are not coaxial withgrooves 32. FIG. 6 shows the component of bow of the side rods in afirst plane, and FIG. 8 shows the component of bow of the side rods in aplane perpendicular to the first plane.

Slide 24 is then moved upwardly between blades 18 and 20 (FIGS. 9, 10,and 11) thereby forcing blades 18 and 2t) apart and in oppositedirections. Side rods 17 are also forced apart thereby stretching andshaping the lateral wire turns 15 into conformity with the shape ofblades 18 and as shown in FIG. 10.

When the side rods 17 are forced apart, the components of bow of theside rods parallel to the directions of movement of blades 18 and 20 arestraightened, as shown by comparison of FIGS. 6 and 9. The components ofbow of the side rods non-parallel to these directions, however, are notstraightened, as shown by comparison of FIGS. 8 and 11. Straightening ofthese latter components of how does not occur because the side walls 31of rectangular groove portions 36 do not engage the sides of the centrallength portions of side rods 17, and do not force these central lengthportions in directions other than the directions of separation of theside rods. During the sizing operation, therefore, only a small amount(as compared with prior art sizing methods) or straightening of the siderods occurs.

Upon removal of the grid 16 from the sizing blades 18 and 20,comparatively little spring-back of the side rods 17 occurs due to thecomparatively little straightening of the side rods during sizing. Somespring-back of the side rods may occur due to the straightening of theside rods in the directions of movement of the sizing blades 18 and 20.It is found, however, that the effects of this latter side rodstraightening and spring-back are generally not so great as tosignificantly impair the quality and usefulness of the sized gridelectrodes. In any event, the reduction in the amount of'straighteuingof the side rods during sizing, and the reduction in the attendantspring-back of 1 the side rods upon removal of the grid from the sizingblades, results in a significant improvement in the quality of gridsmade as compared to grids made according to prior art sizing methods.

Further, during the sizing operation, the side rod portions 40, whichare positioned adjacent the semicircular groove portions 34 when thegrid is mounted on the sizing blades, are engaged along the inner halfof the circumference of the side rods by the walls 31 of groove portions34 and moved into the same positions with respect to each other that theside rod portions 40 assume when the grid is assembled between thespacer plates 44 of an electron tube, as shown in FIG. 12. Therefore,regardless of any spring-back of the side rods 17 when the grid isremoved from the sizing blades, upon assembly of the grid into anelectron tube, the side rod portions 40 will be held in the samerelative positions as they were held during sizing. Holding the side rodportions 40 in the sized position tends to also hold the remaininglengths of the side rods 17 and the lateral wire turns 15 in the sizedposition, thereby providing a high degree of uniformity in the size andshape of the grids from tube to tube.

What is claimed is:

A method of sizing a grid electrode having a pair of spaced-apart siderods and a lateral wire wound around and secured to said side rods, saidmethod comprising:

positioning a pair of forming jaws within said grid electrode, said jawshaving longitudinal grooves matching said side rods at short length endportions and oversize in width at the intermediate portion, moving saidjaws away from each other for engaging inner portions of the side rodsalong the lengths of the side rods and engaging side portions of theside rods only along said short length portions, and continuing themovement of said jaws away from each other until appropriate stretchingand shaping of said lateral wire result and simultaneously the matchinggroove portions act on the short length portions only of the side rodsto dispose them in preselected positions.

References Cited by the Examiner UNITED STATES PATENTS 2,183,635 12/1939Barker 71.5

WILLIAM I. BROOKS, Primary Examiner.

